Preparation of compositions by melt spinning

ABSTRACT

Inorganic compositions were prepared by melt spinning. An inorganic melt was sent to a spinning wheel. As the melt contacts the wheel, it cools and is converted into a solid composition. A melt prepared from lanthanum halide powder and cerium halide powder was converted to a scintillator product of nanoparticles embedded in a glassy matrix.

STATEMENT REGARDING FEDERAL RIGHTS

This invention was made with government support under Contract No.DE-AC51-06NA25396 awarded by the U.S. Department of Energy. Thegovernment has certain rights in the invention.

FIELD OF THE INVENTION

The invention relates to the preparation of inorganic compositions bymelt spinning.

BACKGROUND OF THE INVENTION

Nanostructured materials generally have different electronic, magnetic,optical, and mechanical properties than the corresponding bulkmaterials. Light output from nanophosphors, for example, can be higherthan for micron-sized or larger phosphors. Nanophosphors have attractedinterest due to their potential uses in optics, optoelectronics,lighting, displays, optical amplifiers/scintillators, lasers,microelectronics, tribology, homeland security, radiation detectors,medical imaging, and other applications.

There remains a need for better methods for preparing nanostructuredmaterials.

SUMMARY OF THE INVENTION

In accordance with the purposes of the present invention, as embodiedand broadly described herein, the present invention is concerned with aprocess for preparing a composition. The process includes sending aninorganic melt to a spinning wheel, whereby the melt cools after itcontacts the wheel and is converted into a product that comprisesnanoparticles embedded in a glassy matrix.

The present invention is also concerned with a product prepared by aprocess that comprises sending an inorganic melt to a spinning wheelthat cools the melt after the melt contacts the spinning wheel, wherebythe melt is converted into a product that comprises nanoparticles of acomposition embedded in a glassy matrix of essentially the samecomposition.

The present invention is also concerned with a composition that consistsessentially of nanoparticles of a composition embedded in a glassymatrix of essentially the same composition as that of the nanoparticles.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthe specification, illustrate embodiments of the present invention and,together with the description, serve to explain the principles of theinvention. In the drawings:

FIG. 1 shows a schematic representation demonstrating operatingprinciples of a melt spinner.

FIG. 2 shows results from a differential scanning calorimeter (DSC) runfor lanthanum bromide (LaBr₃) powder.

FIG. 3 shows results from a DSC run for lanthanum chloride LaCl₃)powder.

FIG. 4 shows results from a DSC run for a powder mixture having theformula La_(0.95)Ce_(0.05)Br₃ powder.

FIG. 5 shows results from a DSC run for a powder mixture having theformula La_(0.95)Ce_(0.05)Br_(2.288)Cl_(0.713) powder.

FIG. 6 shows results from a DSC run for a powder mixture having theformula La_(0.95)Ce_(0.05)Br_(1.575)Cl_(1.425) powder.

FIG. 7 shows a transmission electron microscope (TEM) micrograph showingthe microstructure of an embodiment flake of nanoparticles embedded in aglassy matrix of the invention.

FIG. 8 shows an x-ray diffraction (XRD) pattern of an embodiment phaseof LaBr₃:Ce nanoparticles.

DETAILED DESCRIPTION

The present invention provides compositions and methods for preparingthe compositions. The compositions are generally inorganic compositions.Some embodiments of these compositions are phosphors.

Some non-limiting embodiment compositions of the invention include rareearth doped lanthanum fluoride, rare earth doped lanthanum chloride,rare earth doped lanthanum bromide, and rare earth doped mixtures oflanthanum chloride and lanthanum bromide. Some non-limiting embodimentrare earth dopants include cerium, neodymium, europium, thulium,terbium, samarium, gadolinium, dysprosium, and praseodymium. Some othernon-limiting embodiment dopants include thallium, chromium, manganese,titanium, copper, silver, zinc, gallium, antimony, and tellurium.

An embodiment method for preparing the compositions involves the use ofmelt spinning. Melt spinning involves sending a composition in the formof a melt to a spinning wheel. When the melt contacts the spinningwheel, it loses heat and solidifies. A schematic representation showingthe production of the compositions by melt spinning is shown in FIG. 1.Melt spinning apparatus 10 includes crucible 12 filled with powder 14and surrounded by induction heating coils 16. Crucible 12 can be madefrom a material such as, but not limited to, boron nitride, and may beprovided with a coupling (a tantalum coupling, for example) tofacilitate the heating process. Melt spinning apparatus 10 also includesmelt spinning chamber 18 and spinning wheel 20 (a copper wheel, forexample) inside the chamber. During operation, the induction heatingcoils transfer energy to the crucible (a coupler facilitates this,depending on the choice of crucible materials), and powder 14 inside thecrucible heats until it melts. The melt exits the crucible throughopening 22 at the bottom of crucible 12 and moves into melt-spinningchamber 18 where it makes contact with spinning wheel 20. The melt coolsas it contacts the wheel, and is sent through snout 24 where it iscollected as flakes 26. A non-limiting range of speeds of the spinningwheel may be from about 1 rpm to about 5000 rpm, or from about 1000 toabout 3000 rpm, or from about 1000 rpm to about 2000 rpm, or from about1000 rpm to about 1700 rpm. An embodiment composition produced bysending a melt to the spinning wheel may be in the form of flakes thatinclude crystalline nanoparticles in a glassy matrix. The chemicalformula for the crystalline nanoparticle portion of the flakes may beessentially the same as that for the glassy matrix.

Powders may be used as starting materials. A cerium doped lanthanumbromide (LaBr₃:Ce) embodiment composition, for example, may be preparedfrom a mixture of cerium bromide (CeBr₃) powder and lanthanum bromide(LaBr₃) powder. A terbium doped lanthanum chloride (LaCl₃:Tb) embodimentcomposition may be prepared from a mixture of terbium chloride (TbCl₃)powder and lanthanum chloride (LaCl₃). A samarium doped lanthanumbromide/chloride (LaBr_((3-x))Cl_(x):Sm) embodiment composition may beprepared from a powder mixture of samarium bromide (SmBr₃), lanthanumbromide, and lanthanum chloride. A praseodymium doped lanthanum fluoride(LaF₃:Pr) embodiment composition may be prepared from a mixture ofpraseodymium fluoride (PrF₃) and lanthanum fluoride (LaF₃). Otherembodiment compositions include but are not limited to, CeBr₃, YAlO₃:Ce,LuAlO₃:Ce, Lu_(1-x)Y_(x)O₃:Ce, Bi₄Ge₃O₁₂, PbWO₄, CdWO₄, Lu₂SiO₅:Ce,Y₂SiO₅:Ce, Lu_(2-x)Y_(x)SiO₅:Ce, MgF₂:Ce, CaF₂:Ce, BaF₂:Ce, LaCl₃:Ce,K₂LaCl₅:Ce, LaBr₃:Ce, RbGd₂Br₃:Ce, Csl:Na, Csl, Csl:Tl, Nal:Tl, ZnS:Ag,and the like.

The amount of each powder used in preparing an embodiment compositiondepends on the desired amounts of dopant and other ingredients in thecomposition. From the formula of an embodiment composition, the amountof each ingredient can be calculated.

When powders are used, any mixing device or method may be used to mixthe powder. Mixing devices should not generate impurities that remain ina product phosphor composition, or generate only a minimal amount thatdoes not substantially affect properties of the composition. Somenon-limiting examples of methods and devices for mixing powder includemortar/pestle, ball milling, mixer mixing, attrition milling, and jetmilling. Some or all of these methods and devices are employed inindustrial operations. A mill containing spherical or rod-likematerials, for example, may be used as the mixing device. In such amill, the inner wall of the mill and the spherical or rod-like materialscould be made of highly pure (at least 99.9 percent) alumina in order toavoid, or at least minimize impurities in a composition. The surface ofa mixing device that contacts powder precursor could be made of plasticor coated with plastic. Some non-limiting examples of plastics includepolyethylene, polypropylene, polyamides, polyesters and polyurethanes.The use of plastic tends to minimize impurities generated during amixing operation.

After a mixing operation, precursor powder is heated to form a melt. Themelting process can enhance the mixing significantly, and therefore anextensive grinding of powder prior to melting may not be necessary,which may avoid or minimize impurities that tend to result from grindingpowder. When lanthanum halide precursor powder is used, for example, anon-limiting temperature range for heating a melt may be from about 100°C. to about 2800° C., or from about 800° C. to about 950° C.

The melting of precursor powder can take place in a crucible having asmall opening and nozzle. A melt once generated in the crucible can flowthrough the nozzle. The flow through the opening/nozzle can be enhancedusing pressurized gas. Additional mixing action may take place as a meltmoves through the opening/nozzle and out of the crucible. This type ofmixing action is believed to be similar to that of a vortex, which canenhance the uniformity of the components in the melt. The nozzle openingshould be large enough for the melt to flow through, aided with pressurefrom a jet of inert gas (argon, for example). A non-limiting range ofnozzle opening sizes for a crucible may be from about 0.006 to about 0.1inches, or from about 0.01 to about 0.03 inches, or from about 0.010inches to about 0.020 inches. Without wishing to be bound by anyexplanation, it is believed that the mixing, melting and flow of meltthrough the nozzle of a crucible is believed to cause mixing of theprecursor on an atomic scale.

It should be understood that there is no particular restriction on thesize and shape of the crucible. A tube shape with a small opening at thebottom of the crucible, for example, could be used. A crucible with acontinuous feeding device could be used.

It is believed that a uniform distribution of components is formed inthe melt, and that this uniform distribution does not change when themelt contacts the spinning wheel, loses heat, and solidifies. Thecooling provided by the spinning wheel is believed to preventsegregation of a component as particles form after the melt contacts thespinning wheel.

In some embodiments for preparing rare earth doped lanthanum halidecompositions, the temperature of the melt and the rate of spinning of aspinning wheel were such that the product phosphor composition producedwas is in the form of nanoparticles of rare earth doped lanthanum halideembedded in a glassy matrix. In one of these embodiments, flakes ofnanoparticles of cerium-doped lanthanum bromide LaBr₃:Ce embedded in aglassy matrix were prepared by mixing LaBr₃ powder with CeBr₃ powderusing a mortar and pestle under argon in a glove box, loading the powderinto a boron nitride crucible, transferring the loaded crucible to amelt spinner apparatus, melting the powder and injecting the meltthrough a nozzle on the crucible to a spinning copper wheel. The moltenmaterial was forced through the opening using pressurized gas (argon,for example). By using different pressures of the pressurized gas, theflow of the molten material through the opening in the crucible andtherefore the feeding rate of the molten material to the copper spinningwheel can be adjusted.

The viscosity of the molten material can be adjusted by adjusting thetemperature of the molten material. The viscosity also has an effect onthe flow of molten material through the opening in the crucible. Therotation of the spinning wheel promotes cooling of the copper wheel,which is cool before it is exposed to any new molten material. Themolten material is cooled rapidly as it contacts the wheel. As themolten material cools, it forms flakes. In an embodiment, these flakesinclude nanoparticles of cerium doped lanthanum bromide (i.e. LaBr₃:Ce)having an average particle of less than about 100 nanometers (nm)embedded in a glassy LaBr₃:Ce matrix. The LaBr₃:Ce product producedaccording to this embodiment has good light output and energyresolution.

In an embodiment, melt spinning of LaBr₃:Ce results in nanoparticlesLaBr₃:Ce of a uniform size.

In an aspect of the invention related to LaBr₃:Ce formation, LaBr₃:Cenanoparticles having better light output and energy resolution thanconventional methods is obtainable because impurities that typicallyresult from an extensive milling step and from hydrate formation can beminimized or completely prevented,

It should be understood that the choice of lanthanides and dopants arenot limited to lanthanum (La) and cerium (Ce), and that any lanthanidecapable of functioning as an inert host into which an emitting ion maybe doped, may be used with the invention. These include La, Ce, Y, Nd,Cd, W, Mg, Ca, Ba, Na, K, Cs. The host can be any halide, oxyhalide,oxide, nitride, oxynitride, carbide, oxycarbide, or boride. The dopantcan be Ce, Pr, Tm, Tb, Gd, Dy, Cr, Mn, Ti, Cu, Zn, Ga, Sb, Te, Eu, Sm,Y, Tl, Na, Li, B, Ag, or Nd. The choice of lanthanide may be tailored inorder to prepare a chosen nanophosphor having desired emissionproperties.

Some embodiment compositions may be prepared from powders. The amount ofeach powder can be calculated for a desired composition. One example ofa powder composition is one with both LaBr₃ powder and CeBr₃ powder.Another embodiment powder is one with LaBr₃, LaCl₃, and CeBr₃. In someof these, CeBr₃ powder is combined with LaBr₃ powder in a compositionwith a mole percent of cerium in a range of from 0.01 mole percent to 20mole percent. A melt spun product may be one of the formulaLa_(1-x)Br_(3-y)Cl_(y):Ce_(x) wherein x is from 0 to 1, and wherein y isfrom 0 to 3. Both x and y can be fractional numbers. In someembodiments, cerium is not introduced as a bromide but instead it mayintroduced as cerium metal, as an organometallic compound of cerium ascerium oxide, as cerium fluoride, as cerium chloride, as cerium nitrate,or in any other form.

In demonstrating the operability of the invention, raw materials wereused for preparing some embodiment compositions that included LaBr₃,LaCl₃, and CeBr₃ also included some impurities. The amounts of theimpurities were determined using Inductive Coupled Plasma-MassSpectroscopy (ICP-MS). TABLE 1 below provides a listing of theimpurities.

TABLE 1 Impurity LaBr₃ (ppm) LaCl₃ (ppm) CeBr₃ (ppm) Aluminum 21 — —Arsenic 31 — — Barium — — — Boron — — — Bromine — 410 — Cadmium — — —Calcium —  77 67 Copper — — — Gadolinium — — — Iron 16 — — Lanthanum — —21 Magnesium  6 — — Manganese 27 — — Lithium — — — Potassium — — —Sodium — — — Tellurium — — — Thorium  6 — — Titanium — — — Uranium — — —Total 107  487 88According to TABLE 1, CeBr₃ has the lowest content of impurities (totalof less than 100 ppm). Although LaCl₃ had a high impurity content, mostof the impurity is Br, which is a major component of LaBr₃ and so can beused to form a melt with LaBr3 without contributing to the overallimpurity content.

A Differential Scanning Calorimeter (DSC) was used to evaluate reactionsbetween the raw material and crucible materials and to provide guidanceon the melt temperature during melt spinning. A small batch of LaBr₃,LaCl₃, and CeBr₃ raw powders yielding aLa_(0.95)Ce_(0.05)Br_(1.575)Cl_(1.425) composition was mixed using highpurity aluminum oxide mortar and pestle. Powder mixing was performed ina glove box. The mixture powder was added into four different types ofcrucibles including Al₂O₃, BN, Pt, and quartz to investigate thepossibility of reaction between crucible material and raw materials. Theraw material was heated in the crucible to melting in an Ar environmentwith a heating rate of 20° C./min. The results indicate that there is noreaction with any crucible materials including Al₂O₃, BN, Pt, andquartz. These results confirm that Al₂O₃, BN, Pt, and quartz can be usedas crucible materials for melt spinning an inorganic composition.

DSC was performed on the as-received LaBr₃ material (TABLE 1). LaBr₃powders were loaded into the BN crucible inside a glove box, andmoisture content was maintained at less than 50 ppm. The crucible withLaBr₃ powder was quickly transferred to the DSC with BN lid protection.The test was performed with a heating rate of 20° C./min in an Arenvironment. FIG. 2 shows typical DSC result from LaBr₃ powders. As canbe seem from FIG. 2, some moisture that adsorbed on the powder surfacewas removed at about 91° C. In addition, some crystalline water wasremoved at about 372° C. The strong endothermic peak indicates thatLaBr₃ starts to melt at about 788° C.

DSC was performed on the as-received LaCl₃ materials. LaCl₃ powders wereloaded into the BN crucible inside a glove box, and moisture content wasmaintained at less than 50 ppm. The crucible with LaCl₃ powder wasquickly transferred to the DSC with BN lid protection. The test wasperformed with a heating rate of 20° C./min in an Ar environment. FIG. 3shows typical DSC result from LaCl₃ powders. As can be seem from FIG. 3,LaCl₃ has a moisture adsorption at 125° C., however it does not have thecrystalline water at about 400° C. This is an indication that LaCl₃ isless sensitive to the moisture than LaBr₃. The melting point of LaCl₃ isat 877° C.

A small batch of LaBr₃ and CeBr₃ raw powders yieldingLa_(0.95)Ce_(0.05)Br₃ composition was mixed using high purity aluminumoxide mortar and pestle. The mixture powders were also analyzed usingDSC. FIG. 4 shows typical DSC results from LaBr₃ powders with 5 molepercent of CeBr₃. From this figure, one can see that the melting isreduced slightly to about 785° C. due to the eutectic composition. Inaddition to the removal of moisture at about 125 and 400° C., there isadditional moisture removal at about 334° C. Furthermore, the strongerpeak at 334° C. might be an indication that CeBr₃ is much more sensitiveto moisture.

A small batch of LaBr₃, LaCl₃, and CeBr₃ raw powders yielding aLa_(0.95)Ce_(0.05)Br_(2.288)Cl_(0.713) composition was mixed using highpurity aluminum oxide mortar and pestle. FIG. 5 shows typical DSCresults from La_(0.95)Ce_(0.05)Br_(2.288)Cl_(0.713) with LaBr₃/LaCl₃ of75/25 mole ratio. This powder composition has 5 mole percent of CeBr₃.As indicated in FIG. 5, the melting point of theLa_(0.95)Ce_(0.05)Br_(2.288)Cl_(0.713) mixture is lower because of theternary eutectic.

A small batch of LaBr₃, LaCl₃, and CeBr₃ raw powders yielding aLa_(0.95)Ce_(0.05)Br_(1.575)Cl_(1.425) composition was mixed using highpurity aluminum oxide mortar and pestle. FIG. 6 shows typical DSCresults from La_(0.95)Ce_(0.05)Br_(1.575)Cl_(1.425) with LaBr₃/LaCl₃ ina 50/50 mole ratio. This powder composition has 5 mole % of CeBr₃. Asindicated in FIG. 6, the melting point for theLa_(0.95)Ce_(0.05)Br_(1.575)Cl_(1.425) composition has a higher meltingpoint due to the higher amount of high melting point constituent LaCl₃.

The following non-limiting EXAMPLES provide detailed procedures for thepreparation of some embodiment inorganic compositions that are alsoscintillators.

EXAMPLE 1

Preparation of La_(0.95)Ce_(0.05)Br₃. A uniform powder mixture oflanthanum bromide (LaBr₃, 40 grams) and cerium bromide (CeBr₃, 2.11grams) was prepared using a mortar and pestle in a glove box. Theresulting mixture was transferred to a boron nitride crucible. Thecrucible had a nozzle with an opening of 0.019 inches. The crucible andpowder were transferred from the glove box to the induction-heating coilof a melt spinner apparatus. A niobium shield was machined to serve as acoupling from the crucible/powder to the induction coil. The inductioncoil was water cooled to prevent the coil from overheating. After twiceevacuating and purging the system with argon, the induction power wasturned on to melt the powder. The peak temperature was set at 870° C.with a heating rate of about 20° C./min. The copper wheel was turned onand the turning speed was increased slowly to about 1000 rpm. After thetemperature had stabilized for about 2 minutes, a 3 psi jet of argon wasused to inject the molten La_(0.95)Ce_(0.05)Br₃ through the nozzleopening and onto the copper wheel. As the melt contacted the wheel, itwas converted to flakes that sprayed into the snout section thecollecting area. A funnel made out of aluminum foil was made as linerfor the snout to minimize exposure to moisture. The translucent flakeswere collected quickly under argon in a glass container and transferredto a glove box. Yield: about 4 grams. The flakes appear to beagglomerates held loosely together because they break up easily. FIG. 7shows a TEM micrograph of the flaky product. As can be seen from FIG. 7,the flakes include large numbers of small particles of a size on theorder of about 20 nm. According to the diffused rings of the diffractionpattern, the product is a composition of La_(0.95)Ce_(0.05)Br₃nanoparticles that are embedded in a glassy LaBr₃:Ce matrix.

EXAMPLE 2

Preparation of La_(0.95)Ce_(0.05)Br₃. A uniform powder mixture of LaBr₃(40 grams), LaCl₃ (8.64 grams), and CeBr₃ (2.11 grams) was preparedinside a glove box using a mortar and pestle made of high purityaluminum oxide. The mixture was poured into a boron nitride crucibleinside the glove box, and then loaded into an induction-heating coil ina melt spinner apparatus. A tantalum (Ta) shield was machined to serveas a coupling to the induction coil. The induction coil was water cooledto prevent the coil from overheating. The apparatus was evacuated andthen purged with argon. After repeating the evacuation/purging processto minimize the presence of oxygen and moisture, the induction power wasturned on to heat up the powder. The apparatus peak temperature was setat 870° C. with a heating rate of about 20° C./min. The copper wheel wasturned on and the turning speed was increased slowly to about 2000 rpm.After the temperature had stabilized for about 2 minutes, an argon jetof 1 psi was applied to inject the molten La_(0.95)Ce_(0.05)Br₃ throughthe nozzle opening and onto the copper wheel. The opening of the BNnozzle was about 0.019″. The nozzle was lowered to toward the copperwheel, which reduced the distance between the nozzle and the copperwheel. Due to the small distance between the nozzle and the wheel, allof the melt was splashed randomly instead of going into the snout area.The splashed products were chunky with irregular structure. FIG. 8 showsan X-ray diffraction pattern of the product.

An x-ray diffraction (XRD) spectrum of the nanoparticle composition ofEXAMPLE 6 is shown in FIG. 8. The XRD pattern of LaX₃:Ce shows theexpected lines of the tysonite structure, and the absence of other linesindicates high phase purity.

EXAMPLE 3

Preparation of La_(0.95)Ce_(0.05)Br_(2.288)Cl_(0.713). A uniform powdermixture of LaBr₃ (40 g), LaCl₃ (8.64 g) and CeBr₃ (2.11 g) was preparedin a glove box using a mortar and pestle. The powder mixture wastransferred to a boron nitride crucible. The crucible had a nozzleopening of 0.019 inches. The crucible and powder were transferred to theinduction-heating coil of a melt spinner apparatus. A niobium shield wasmachined to serve as a coupling to the induction coil. The inductioncoil was water cooled to prevent the coil from overheating. After twiceevacuating and purging the system with argon, the induction power wasturned on to melt the powder mixture. The peak temperature was set at870° C. with a heating rate of about 20° C./min. The copper wheel wasalso turned on and the turning speed was increased slowly to about 1700rpm. After the temperature had stabilized for about 2 minutes, a 1 psijet of argon was used to inject the molten La_(0.95)Ce_(0.05)Br₃ throughthe nozzle opening and onto the copper wheel. As the melt contacted thewheel, it was converted to solid flakes. The flakes were sprayed intothe snout section of the collecting area. The flakes were collectedquickly under argon in a glass container and transferred to a glove box.Yield: about 10 grams.

EXAMPLE 4

Preparation of La_(0.95)Ce_(0.05)Br_(2.288)Cl_(0.713). The procedure ofEXAMPLE 3 was followed with the exception that a tantalum shield wasused instead of a niobium shield, and the speed of the rotating wheelwas about 2000 rpm instead of 1700 rpm. Yield: about 12 grams.

EXAMPLE 5

Preparation of La_(0.95)Ce_(0.05)Br_(2.288)Cl_(0.713). The procedure ofEXAMPLE 3 was followed with the exception that a tantalum shield wasused instead of a niobium shield, the speed of the rotating wheel wasabout 2000 rpm instead of 1700 rpm, and the nozzle opening of thecrucible was 0.010 inches instead of 0.019 inches. The melt-spun flakeswere much smaller and had a finer texture than those of EXAMPLE 3 orEXAMPLE 4.

EXAMPLE 6

Attempted preparation of La_(0.95)Ce_(0.05)Br_(2.288)Cl_(0.713) using acrucible with a very small nozzle opening. The procedure of EXAMPLE 4was repeated with the exception that the nozzle opening was 0.005inches. At a peak temperature of 870° C. and an argon jet pressure ofabout 1 psi, no melt could be injected out of the nozzle. When the argonjet pressure was increased to about 12 psi, still no melt could beinjected. When the melt temperature was increased to about 1300° C. withan argon jet pressure of 12 psi, still no melt could be injected throughthe nozzle.

Some embodiment compositions are phosphors that may be used forradiation detection. Large-area radiographic devices are often based ontiled mosaics of single crystals or an array of single crystal pixels.These devices suffer from disadvantages associated with non-uniformlight output over the large area of the detector, and from the darkcontrast lines that result from the seams between the tiles or pixels.Another significant problem associated with the production of pixelateddetectors relates to the difficulty in producing pixels; some materials,such as the known scintillator Gd₂SiO₅:Ce (GSO:Ce) single crystals aremicaceous and cannot be easily cut into pixels and polished for use inradiographic imaging. By contrast, embodiment compositions of thisinvention are expected to have a relatively uniform light output, can bemade seamless over a large area. They can be used in detectors forproton and neutron radiography, for positron emission tomography, andfor medical radiography. Relatively inexpensive, large area detectors(portal monitors, shipping containers, medical imagers, and the like)are possible because the process for making embodiment phosphorcompositions can be scaled up to form large amounts of the compositions.The compositions may be used in radiation detectors for interrogation ofcomplex and irregular shapes.

By selecting the appropriate rare earth dopant, the light emission fromthe radiation detector can be tailored for either a photomultiplier or aphotodiode.

The EXAMPLES described above involve preparation of a product using abatch type process on a relatively small scale. It should be understoodthat the process could be scaled up so that much greater amounts ofproduct could be obtained. In addition, the process could be changedfrom a batch type to a continuous type process. This could beaccomplished by using, for example, a continuous feed mechanism such asa screw feed for continuously delivering powder at a controlled rateinto the melt crucible. Such a feeder would be used with an airlocksystem for delivering powder without opening the melt spinner to theatmosphere. A larger crucible with multiple ejection nozzles would beused. The crucible could be heated by induction heating, resistanceheating, or by using radiant heat. A wheel large enough to accommodatethe multiple ejection nozzles would be used. The wheel would be activelycooled using, for example, water or gas. A continuous or batch removalsystem that allows product to exit the melt spinner without letting airinto it would also be used.

In summary, inorganic compositions were prepared by sending an inorganicmelt to a spinning wheel. Some of the products were shown to benanostructured, having nanoparticles embedded in a glassy matrix.

The foregoing description of the invention has been presented forpurposes of illustration and description and is not intended to beexhaustive or to limit the invention to the precise form disclosed, andobviously many modifications and variations are possible in light of theabove teaching.

The embodiments were chosen and described in order to best explain theprinciples of the invention and its practical application to therebyenable others skilled in the art to best utilize the invention invarious embodiments and with various modifications as are suited to theparticular use contemplated. It is intended that the scope of theinvention be defined by the claims appended hereto.

1. A process for preparing a composition, comprising: sending aninorganic melt to a spinning wheel, whereby the melt cools after itcontacts the wheel and is converted into a product that comprisesnanoparticles embedded in a glassy matrix.
 2. The process of claim 1,wherein the step of sending the inorganic melt to a spinning wheelfurther comprises sending the inorganic melt through a narrow nozzle. 3.The process of claim 1, wherein the product comprises a scintillator. 4.The process of claim 1, wherein the inorganic melt is sent to thespinning wheel under an inert atmosphere that comprises argon, nitrogen,helium, or mixtures thereof.
 5. The process of claim 1, wherein theinorganic melt is sent to the spinning wheel in a continuous process. 6.The process of claim 1, wherein the inorganic melt is sent to thespinning wheel in a batch type process.
 7. The process of claim 1,wherein the inorganic melt comprises Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca,Sr, Ba, Ra, B, C, N, O, F, Cl, Br, I, At, Al, Si, P, S, Sc, Ti, V, Cr,Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd,Ag, Cd, In, Sn, Sb, Te, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi,Po, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, orcombinations thereof.
 8. The process of claim 1, wherein the inorganicmelt comprises an oxide, a nitride, an oxynitride, a sulfide, aphosphide, a selenide, a carbide, an oxycarbide, a boride, a halide, anoxyhalide, an organometallic compound, or combinations thereof.
 9. Theprocess of claim 1, further comprising forming an inorganic melt from apowder mixture comprising lanthanum halide and rare earth material. 10.The process of claim 9, wherein the weight ratio of lanthanum halidepowder to rare earth material is in a range of from about 10,000:1 toabout 1:100.
 11. The process of claim 8, wherein the lanthanum halidecomprises lanthanum fluoride, lanthanum chloride, lanthanum bromide,lanthanum iodide, or mixtures thereof.
 12. The process of claim 1,wherein the solid composition is of the formulaM_(1-x)Br_(3-y)Cl_(y):Q_(x), wherein M is a lanthanide or an actinide,wherein x is less than or equal to one, wherein Q is a rare earthelement, and wherein y is less than or equal to
 3. 13. The process ofclaim 12, wherein M is chosen from yttrium, lanthanum, gadolinium,lutetium, and combinations thereof.
 14. The process of claim 12, whereinQ is chosen from cerium, samarium, europium, terbium, and praseodymium.15. A product prepared by a process that comprises sending an inorganicmelt to a spinning wheel that cools the melt after the melt contacts thespinning wheel, whereby the melt is converted into a product thatcomprises nanoparticles of a composition embedded in a glassy matrix ofessentially the same composition.
 16. The product of claim 15, whereinsaid product comprises a scintillator.
 17. The product of claim 15,wherein said product is of the formula M_(1-x)Br_(3-y)Cl_(y):Q_(x),wherein M is a lanthanide or an actinide, wherein x is less than one,wherein Q is a rare earth element, and wherein y is less than or equalto
 3. 18. The product of claim 15, wherein M is chosen from yttrium,lanthanum, gadolinium, lutetium, and combinations thereof.
 19. Theproduct of claim 17, wherein Q is chosen from cerium, samarium,europium, terbium, and praseodymium.
 20. The product of claim 15,wherein the product comprises Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba,Ra, B, C, N, O, F, Cl, Br, I, At, Al, Si, P, S, Sc, Ti, V, Cr, Mn, Fe,Co, Ni, Cu, Zn, Ga, Ge, As, Se, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd,In, Sn, Sb, Te, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Po, La,Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, or combinationsthereof.
 21. The product of claim 15, wherein said product comprises ahalide, an oxide, a nitride, an oxynitride, a sulfide, a phosphide, aselenide, a carbide, an oxycarbide, a boride, a halide, an oxyhalide, anorganometallic compound, or combinations thereof.
 22. The product ofclaim 15, wherein said product comprises CeBr₃, YAlO₃:Ce, LuAlO₃:Ce,Bi₄Ge₃O₁₂, PbWO₄, CdWO₄, Lu₂SiO₅:Ce, Y₂SiO₅:Ce, MgF₂:Ce, CaF₂:Ce,BaF₂:Ce, LaCl₃:Ce, K₂LaCl₅:Ce, LaBr₃:Ce, RbGd₂Br₃:Ce, Csl:Na, Csl,Csl:Tl, Nal:Tl, ZnS:Ag, or combinations thereof.
 23. The product ofclaim 15, wherein said product comprises nanoparticles.
 24. Acomposition that consists essentially of nanoparticles of a compositionembedded in a glassy matrix of essentially the same composition as thatof the nanoparticles.
 25. The composition of claim 23, wherein saidcomposition is of the formula M_(1-x)Br_(3-y)Cl_(y):Q_(x), wherein M isa lanthanide or an actinide, wherein x is less than or equal to one,wherein y is less than or equal to
 3. 26. The composition of claim 23,wherein M is chosen from yttrium, lanthanum, gadolinium, lutetium, andcombinations thereof.
 27. The composition of claim 23, wherein Q ischosen from cerium, samarium, europium, terbium, and praseodymium.